1. Field of the Invention
The present invention relates to an ink jet ink, an ink cartridge having such an ink and an ink jet recording method using the ink.
2. Description of the Related Art
In order to improve the fastness of a resulting image, an ink to which a polyurethane polymer is added has heretofore been investigated (Patent Literature 1: Japanese Patent Application Laid-Open No. 2011-144354). Patent Literature 1 describes an ink containing a self-dispersion carbon black and a polyurethane polymer which contains a polyether polyol as a constituent component.
On the other hand, in order to improve the storage stability of an ink, an ink jet ink containing an antioxidant has been investigated (Patent Literature 2: Japanese Patent Application Laid-Open No. 2009-287014). Patent Literature 2 describes that 2,6-di-tert-butyl-p-cresol (BHT) which is a general-purpose antioxidant is contained in an ink containing a pigment and a compound having an ethylene oxide structure.
As a result of an investigation by the present inventors, it has been found that the ink containing the self-dispersion carbon black and the polyurethane polymer having the polyether polyol as a constituent unit causes a change in the fastness of the resulting image before and after long-term storage. Specifically, when the image was stored for a long period of time, the fastness of the image was lowered. Thus, BHT which is a general-purpose antioxidant was used in the ink described in Patent Literature 1 with reference to Patent Literature 2. As a result, the lowering of the fastness of the image when stored for a long period of time was inhibited. However, when this ink has was in an ink jet recording method in which an ink is ejected from a recording head by causing thermal energy to act on the ink, the ejection stability of the ink was low. When the recording was conducted at high speed in particular, the lowering of the ejection stability of the ink was marked.